We propose to extend previous studies of the clinical utility of diagnostic x-rays in two important ways: a) We will prospectively measure the clinical utility of the oral cholecystogram (OCG) and the gallbladder ultrasound in clinical practice and use data from this study to develop decision rules based on the history and physical examination, designed to improve the evaluating of patients with suspected gallbladder disease. b) We will measure the effect on provider behavior and patient outcome, of applying previously developed decision rules for the upper gastrointestinal series (UGI). Measurement of OCG utility will be performed by prospectively gathering a standard data base on a large number of patients undergoing either an OCG or a gallbladder ultrasound, and by then following the patients to determine diagnostic and clinical outcome. The relationship of the two diagnostic tests to changes in diagnosis, therapy and outcome may then be assessed. Decision rules, designed to predict these endpoints and based on the history and physical examinations will then be created. The other phase of the study will involve the controlled introduction of a set of UGI decision rules designed to decrease use of the UGI without compromising patient care. Providers in several settings will be randomly assigned to receive instructions on the use of these rules. Outcomes will be assessed by measuring provider diagnostic accuracy, patient outcomes and the number of UGI's ordered by each provider. We hope to demonstrate that easily obtained clinical information has a high information value and can be used to improve the use of selected diagnostic tests. The end result might then be a decrease in the cost of care without a decrease in quality.